MOSCOW (Bloomberg) - Russia warned that it may treat US-led coalition aircraft over Syria as targets following the shooting down of a Syrian government warplane, in an escalation of rhetoric between the two rivals in the Middle East conflict.

The downing of the aircraft was "a cynical violation of Syria's sovereignty", the Russian Defence Ministry said in an e-mailed statement on Monday (June 19).

In response, "Russia's ground and air defenses will track any air targets, including the international coalition's planes and drones, found to the West of the Euphrates river," the ministry said, adding that it is halting the so-called deconfliction coordination with the US aimed at averting air incidents.

The Su-22 jet was shot down on Sunday (June 18) by a US F-18 fighter as an act of "collective self-defence of coalition-partnered forces" after the Syrian aircraft dropped bombs close to American-backed fighters near the northern Syrian town of Tabqah, according to a US-led coalition statement.

"The Coalition does not seek to fight Syrian regime, Russian, or pro-regime forces partnered with them, but will not hesitate to defend Coalition or partner forces from any threat," it said.

The Defence Ministry statement doesn't mean there'll be war with the US, though it's a "pretty serious" signal that Russia won't accept acts of aggression against Syria, said Frants Klintsevich, deputy head of the defence committee in Russia's Upper House of Parliament.

The US is "tough when nobody touches them, but immediately become normal people after getting slapped in the face", he said.

Russia first halted the deconfliction agreement in April after the US carried out air strikes on Syrian targets. Defence Minister Sergei Shoigu later said that the mechanism to avert conflict in the skies between Russian and US-led forces continues to operate despite a formal end to the pact.